diff --git a/src/protocol/eval/error.rs b/src/protocol/eval/error.rs
index 81128b445a5c36ed8cda7034b2ca9d2f99084a8e..488097f6357b6d5e67f9d2eb2fd3fa387a06c09d 100644
--- a/src/protocol/eval/error.rs
+++ b/src/protocol/eval/error.rs
@@ -10,7 +10,7 @@ use super::executor::*;
 /// Represents a stack frame recorded in an error
 #[derive(Debug)]
 pub struct EvalFrame {
-    pub line: u32,
+    pub line: Option<u32>,
     pub module_name: String,
     pub procedure: String, // function or component
     pub is_func: bool,
@@ -24,10 +24,15 @@ impl fmt::Display for EvalFrame {
             "component"
         };
 
+        let line_str = match self.line {
+            Some(line_number) => line_number.to_string(),
+            None => String::from("??"),
+        };
+
         if self.module_name.is_empty() {
-            write!(f, "{} {}:{}", func_or_comp, &self.procedure, self.line)
+            write!(f, "{} {}:{}", func_or_comp, &self.procedure, line_str)
         } else {
-            write!(f, "{} {}:{}:{}", func_or_comp, &self.module_name, &self.procedure, self.line)
+            write!(f, "{} {}:{}:{}", func_or_comp, &self.module_name, &self.procedure, line_str)
         }
     }
 }
@@ -50,7 +55,7 @@ impl EvalError {
         for frame in prompt.frames.iter() {
             let definition = &heap[frame.definition];
             let statement = &heap[frame.position];
-            let statement_span = statement.span();
+            let statement_span = statement.maybe_span();
 
             // Lookup module name, if it has one
             let module = modules.iter().find(|m| m.root_id == definition.defined_in).unwrap();
@@ -62,7 +67,7 @@ impl EvalError {
 
             last_module_source = &module.source;
             frames.push(EvalFrame{
-                line: statement_span.begin.line,
+                line: statement_span.map(|v| v.begin.line),
                 module_name,
                 procedure: definition.identifier.value.as_str().to_string(),
                 is_func: definition.kind == ProcedureKind::Function,